Implementation of the CDKN1C gene study within scope of diagnosis of the Beckwith-Wiedemann Syndrome

• Autor(a) principal: Faria, Ana Margarida Torres Pereira
• Data de Publicação: 2023
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10348/11982
• topic: Molecular Genetics; Imprinting Disorders

Imprinted genes are involved in diverse and essential biological processes including embryonic and fetal growth, brain development and adult metabolism. Therefore, inappropriate expression of imprinted genes has a significant impact on growth, brain function, behaviour as well as hormonal and metabolic systems, all of which are frequently associated with complex syndromes. Beckwith-Wiedemann Syndrome (BWS; OMIM #130650) is an autosomal dominant rare multisystem human genomic disorder with variable clinical expression and complex molecular aetiology. The most prevalent manifestations of BWS are macroglossia, overgrowth, hemihypertrophy, omphalocele and other abdominal wall defects and various abnormalities of the cardiac, digestive and urinary systems. Another important factor to consider is the increased predisposition for embryonal tumours including Wilms tumour, hepatoblastoma, adrenocortical carcinoma, and neuroblastoma. The main cause of this syndrome is the deregulation of imprinted genes in the 11p15 region, in particular changes in methylation in differentially methylated regions that lead to alterations in the relative contribution of parental alleles. However, when the analysis of methylation pattern in patients reveals normal results, other causes may be taken into account. Thus, one approach is the screening for variants in genes located in the 11p15 region. In the context of this syndrome, CDKN1C is an interesting gene to investigate due to the pathogenic variants in the gene associated with BWS diagnosis and correlations with specific clinical features. The CDKN1C gene is a negative regulator of cell proliferation that comprises three exons, two of which are protein coding (p57KIP2). It inhibits cyclin-dependent kinase (CDK) complexes during the G1 phase of the cell cycle. CDKN1C is also an imprinted gene localized in the short arm of chromosome 11 (11p15.4) and is monoallelically expressed by the maternal allele in the majority of organs. The main objective of this project was the implementation of CDKN1C gene study in a cohort of patients with clinical suspicion of Beckwith-Wiedemann Syndrome in which MS-MLPA revealed normal results in terms of gene copy number and imprinting status at 11p15 region. The screening for CDKN1C gene variants was performed by PCR amplification followed by Sanger Sequencing. Results obtained through a bioinformatics analysis revealed that the detected variants have no clinical significance that justifies the previously suspected clinical diagnosis of BWS. Nevertheless, the implementation of the CDKN1C gene study was successfully completed. Since the main objective of this thesis was its clinical usefulness in diagnosis, in an attempt to add relevant information and increase correlations towards a positive diagnosis of BWS, a compilation was made of pathogenic variants in the CDKN1C gene associated with BWS and a flowchart was adapted, establishing a concise diagnostic line based on the international consensus established for this syndrome. As a result, a table is presented that compiles all pathogenic variants reported in databases and published in scientific articles with the different parameters investigated.